Fibrous structures with labile active substance

ABSTRACT

A fibrous structure comprising a fibrous matrix with immobilized surrogate particles, is provided. A labile active substance is selectively deposited on the immobilized surrogate particles. In one embodiment, the surrogate particles are porous and have surface cavities, and the labile active substance is deposited in the pores and surface cavities. In another embodiment, the labile active substance is in attractive association with or attached to the surrogate particles.

FIELD OF THE INVENTION

This invention relates to a fibrous structure with immobilizedparticles.

BACKGROUND OF THE INVENTION

Particulate carriers for sorptive impregnants are known. Exemplary areconventional relatively thermostable, sorptive impregnants such ascopper and silver salts, on activated carbon particles. Also known areliquid sorptive impregnants such as liquid amines, on particulatecarriers. Illustrative are U.S. Pat. Nos. 5,145,820 and 5,462,908 toLiang et al, which describe the deposition of liquid sorptive amines onactivated carbon particles by reduced pressure sublimation.

Fibrous structures containing adsorptive particles are commerciallyavailable. Filter media or filters made from these structures includesorptive particles for selectively removing certain components of aliquid or gas passing through the filter. Acceptable performance withlow pressure drop beneficially results from the sorptive particles beingdistributed in a three dimensionally spaced apart arrangement and beingimmobilized in this arrangement. However, the immobilizing step can bedetrimental to sorptive particles. For example, physical immobilizationtechniques such as needling and water jet entangling, can adverselyaffect sorptive particles.

On the other hand, if heat-bonding is used for immobilizing the sorptiveparticles, the elevated temperature applied for the bonding could beharmful. Furthermore, chemically aggressive particles could adverselyaffect the fibrous structure during an elevated heat-bonding step. Inaddition, moisture in active particles can interfere with heat-bonding.Moreover, there is difficulty in regenerating the functional activity ofa fibrous structure having active particles bonded to the fibrousstructure.

Accordingly, despite prior advances in this art, an improved fibrousstructure having a three dimensional arrangement of immobilized activematerial, is needed. Such a fibrous structure could beneficially includeactive material adversely affected by an immobilization step.Furthermore, such a fibrous structure could advantageously includechemically aggressive, active material. In addition, such a fibrousstructure would facilitate the recovery and safe disposal of spentactive material, and the regeneration of the functional activity of thefibrous structure.

SUMMARY OF THE INVENTION

In accordance with the present invention, an improved fibrous structureis beneficially based upon a fibrous matrix and surrogate particlessupported by the fibrous matrix. By "surrogate particles" is meantparticles that function as a carrier for an active substance. Thesurrogate particles may be porous and may have surface cavities.

In accordance with the invention, the surrogate particles arebeneficially distributed in a three dimensional arrangement andimmobilized. Advantageously, the fibrous matrix is generally uniform instructure, and the three dimensional arrangement is also generallyuniform.

In accordance with the invention, a labile active substance is carriedby the surrogate particles, and there is selective deposition of thelabile active substance on the surrogate particles. The selectivedeposition can be based upon features such as the physical structure ofthe surrogate particles, or an attractive association or an attachmentof the labile active substance to the surrogate particles. Thus, forexample, an active substance sensitive to thermally-effected, surrogateparticle immobilization, may be selectively deposited on the surrogateparticles after surrogate particle immobilization by heat-bonding.

The labile active substance may be merely deposited on, or may be inattractive association with or attached to, the surrogate particles. Ifin attractive association or attached, the attraction or attachment maybe reversible so that spent labile active substance can be recoveredwithout affecting the surrogate particles/fibrous structure, and theactivity of the fibrous structure may thereafter be regenerated. Thelabile active substance selected may provide the fibrous structure witha purifying or odorizing activity, processing benefits, or analyticaluses.

BRIEF DESCRIPTION OF THE DRAWING

Reference is now made to the accompanying drawing, which is highlyillustrative, and forms a part of the specification of the presentinvention.

FIG. 1 is a sectional view depicting a fibrous structure havingimmobilized particles, in accordance with the invention; and

FIG. 2 is an enlarged view of an immobilized surrogate particle havingsurface cavities and pores, and entrapped within an interstitial spaceof, and bonded to fibers of, a fibrous structure similar to that of FIG.1.

DETAILED DESCRIPTION OF THE INVENTION

As indicated above, the fibrous structure of the present invention isadvantageously based upon a fibrous matrix with surrogate particlesdistributed and immobilized in a three dimensional arrangement. Such astructure will be typically non-woven, and may be made using compositefibers, a mixture of structural fibers and fusible fibers, powderbonding, or using other suitable approaches for bonding the surrogateparticles to the fibrous structure. Immobilization of the surrogateparticles may also be accomplished by physical techniques such asneedling and water jet entangling.

In any event, the fibrous matrix will include a structural fibrouscomponent, and beneficially the structural component will providestructural integrity even when the fibrous matrix is highly loaded withthe surrogate particles. If heat is used for immobilizing the surrogateparticles, the bonding temperature will typically be an elevatedtemperature in the range of from about 130 to 200° C., although anelevated temperature outside this range may be appropriate dependingupon factors including the specific material for bonding the surrogateparticles to the fibrous matrix.

To provide for point-of-contact bonding of the surrogate particles tothe fibrous matrix, the fibrous matrix is preferably formed fromcomposite fibers having a structural fiber component and a heat-bondablefiber component. Generally speaking, the structural component willtypically melt at a temperature at least about 30 to 50° C. higher thanthe heat-bondable component. Preferably, the heat-bondable fibercomponent has high bonding capability for bonding the surrogateparticles to the fibrous matrix. The bonding is preferably achieved byheating a heat-bondable, polymeric fiber component to a temperature atwhich it is tacky or molten, but in any event provides for adhesion.Beneficially, the heating will also provide for stabilization of the webstructure by fiber-fiber bonding at the cross over points of fibers. A"spot weld" is produced by adhesion at the point of contact ofindividual surrogate particles with individual matrix fibers.Point-of-contact bonding advantageously minimizes undesirable coating ofthe surrogate particles by the bonding material.

Concentric sheath-core fibers are one example of useful compositefibers. Suitable composite fibers also include eccentric sheath-corefibers, and fibers having a side-by-side configuration. Composite fibersof these types are known as bicomponent or heterofil fibers. One skilledin the art will recognize that a variety of multiconstituent fiberstructures having a lower melting component exist or may be made, andwill recognize that those multiconstituent fiber structures may beselected from, as useful composite fibers.

Useful fibers may be in a variety of forms including crimped andnon-crimped cut staple fibers, shortcut staple, continuous filaments,and blends thereof. Advantageously, a non-woven web structure inaccordance with the invention, may be dry-formed from crimped, staplefibers so as to be lofty. In addition, spunbond web structures and meltblown web structures may be used.

The structural fibers should be present in an amount sufficient toprovide a matrix structure and ample surface area for immobilization ofthe surrogate particles. Typically, the fibrous matrix will be presentin a minor amount compared to the loading of the surrogate particles.Although a fibrous web including surrogate particles may include fromabout 5% to 80% by weight of structural fiber, usually only about 10 to25 wt. % will be structural fiber unless low density surrogate particlesare used.

The matrix structure will preferably be generally uniform to assist in apreferred, three dimensionally generally uniform distribution andspacing of the surrogate particles, with adequate void space. Inaddition to promoting generally uniform application and deposition ofthe active substance on the surrogate particles, this benefitsaccessibility of the deposited active substance to a liquid or gas.Tortuous flow paths may be provided by the three dimensionally spacedapart arrangement of the surrogate particles.

An open, generally uniform, non-woven web structure in accordance withthe invention, may be beneficially dry-formed from crimped, staplemacrofiber having an average diameter in excess of about 10 microns. Theaverage diameter will typically range from about 12 to 25 micronsdepending upon the intended application. If desired, structural fibersof significantly different diameters may be combined to form the fibrousmatrix.

For dry lay processing, the structural fiber will generally have alength to diameter ratio that is limited on the low side. On the highside, continuous length fiber may be used. For wet lay processing, ifused, an appropriate length to diameter ratio of the structural fiberwill be selected.

Useful fibrous structures can be built to thicknesses of from about 0.5to 50 mm. However, if desirable depending upon considerations includingthe end use, much thicker structures can be made. Stacked fibrousstructures can be made.

The fibrous matrix may also include a structurally beneficial amount ofstiffening fibers having a denier per filament of from 6 to 10,000especially if the surrogate particles are relatively large in size. Inaddition, the fibrous matrix may include microdenier fibers for removalof relatively smaller particles from a gas or liquid. These stiffeningfibers or microdenier fibers may be composite or non-composite fibers ora blend thereof. The fibrous matrix may include other fibers or filamentor fibrets, depending upon the result desired.

The surrogate particles may be any particles, organic or inorganic,suitable as a carrier for an active substance. Useful surrogateparticles advantageously include structural features that assist thedeposition of the active substance, and in particular selectivedeposition on the surrogate particles vis-a-vis the fibrous matrix.Exemplary are porous particles, and particles having a rough orirregular surface providing surface cavities or recesses. As illustratedin FIG. 2, useful surrogate particles may be porous and have surfacecavities. The surrogate particles may have a useful functional activitysuch as sorptive activity, but to be useful in this invention, it is notnecessary that the surrogate particles function other than as a carrierfor the active substance. Also, it is not necessary that usefulsurrogate particles be porous or have surface cavities. Exemplarysurrogate particles include carbon particles such as activated carbon,zeolite particles, alumina particles such as activated alumina,polymeric particles including, for example, styrene monomer, andabsorbent particles such as commercially available superabsorbentparticles. Useful porous polymeric particles advantageously have voidvolumes greater than about 50%, beneficially of about 60 to 65% or more.Particularly suitable polymeric particles are available from BioporeCorporation under the trademark MAGNAPORE, and are low density particleswith void volumes greater than 70%, typically about 90% or more, andhave cavities ranging in diameter from about 1 to 100 microns, andinterconnected by pores. The foregoing description is intended to berepresentative of and not in limitation of particles suitable for use assurrogate particles in the practice of the present invention.

In accordance with the invention, the surrogate particles areimmobilized. Heat-bonding beneficially limits migration of the surrogateparticles within the structure, as well as loss from the structure.Bonding of individual surrogate particles to the fibrous matrix at morethan one point is advantageous. Heat-bonding may be achieved by, forinstance, the addition to the fibrous web of surrogate particles heatedto an appropriate elevated temperature, or by heating the web to anappropriate elevated temperature after the surrogate particles have beenadded to the web. The immobilized surrogate particles may be only on theweb surface, or within the web, or on the web surface and within theweb.

The surrogate particles will typically have an average size in the rangeof from about 10 microns, typically about 100 microns, to about 3 mm to5 mm, may be in the form of beads, granules and so forth, and may varyin shape from spheroidal particles to irregularly shaped particles.Generally speaking, the surrogate particles have an appropriate size tobe entrapped by the web structure. However, the surrogate particles mayalso be deposited by being preheated to an elevated temperature.

The surrogate particles may be elongated, and more particularly may bein the form of fibers, in particular synthetic fibers, havinglongitudinally disposed surface channels for the selective deposition ofthe active substance. If in the form of fibers, the surrogate particleswill be physically distinct from the structure-forming fibers of thefibrous matrix.

The fibrous matrix may be loaded with about 20% to 95% by weight of thesurrogate particles, based on the combined weight of the surrogateparticles and of the matrix fiber. In selecting the loading,consideration should be given to providing adequate surface area fordeposition of the labile active substance. Because the surface area of aparticle depends not only upon the density of the particle, a higherweight percent loading of one type of surrogate particle than anothertype of surrogate particle, would not necessarily result in more surfacearea for deposition. Thus, a high loading of low density surrogateparticles could result in adequate surface area for deposition, yetconstitute only a low weight percent, for instance, 25 wt. %. Ifsurrogate particles similar in density to activated carbon or zeolite oralumina are chosen, the fibrous matrix will typically be loaded withabout 50% to 90% by weight of the surrogate particles, depending, ofcourse, upon in particular the surface area requirements for deposition.Generally speaking, a relatively higher volume of the fibrous matrixoccupied by the surrogate particles, will provide for tortuous flowpaths in the fibrous matrix.

In accordance with a benefit of the invention, the active substancecarried by the surrogate particles, may be a labile active substance.Although a variety of active substances having a useful function may beused, a beneficial labile active substance will typically function in afibrous structure in accordance with the invention, to remove certaincomponents or undesirable contaminants from, or be released into, a gasor liquid; or to act upon the gas or liquid or a component or componentsthereof with which the labile active substance is in contact, to producea useful processing effect such as an alteration, change or chemicalmodification; or to analyze the gas or liquid, or effect a usefulseparation. If released, the release will usually be at a desirably slowrate from the surrogate particles. Useful processing effects includekilling or inactivating or attenuating harmful bacteria and viruses, andchemically modifying undesirable inorganic contaminants. Useful analysesinclude diagnostic tests. The function of the labile active substancemay be enhanced by functional activity of the surrogate particles or byfunctional activity of another substance or material. The labile activesubstance will be selected depending upon the end use or functionalactivity desired.

Prior to deposition on the surrogate particles, the labile activesubstance may be in solid, liquid or vapor form. The term "labile"excludes relatively stable substances such as conventional copper, zincand silver sorptive impregnants. A useful labile active substance willgenerally be functionally labile or associatively labile. By"functionally labile" is meant sensitive to loss or diminution of theuseful function; and by "associatively labile" is meant volatile,sublimable, or otherwise subject to loss from the surrogate particles tothe atmosphere. Lability may be caused by the application of elevatedheat, that is, heat in excess of about 100° C. Lability may relate tothe physical form in which the active substance is carried, forinstance, as a liquid. Lability may result from the manner in which theactive substance is carried by the surrogate particles, or may resultfrom or be caused by other factors. A thermolabile active substance maybe sensitive to heat-bonding of the surrogate particles to a fibrousmatrix, as a result of being functionally labile or associativelylabile.

Exemplary labile active substances include liquid and solid, organic andinorganic compounds such as potassium permanganate, activated manganesedioxide, alkali metal and alkaline earth metal iodates, sorptive organicamines, substances intended to be released such as fragrances, biocides,and labile catalysts and other processing and analytical agents. Usefulsorptive organic amines include substituted liquid amines such asaliphatic primary, secondary and tertiary amines. Exemplary sorptiveorganic amines include diethylenetriamine, ethylenediamine,triethylenediamine, isopropylamine, diisopropylamine, piperidine,dipropylamine, triethylamine and triisobutylamine. Another useful liquidis polyethyleneglycoldimethylether, which is commercially available fromHoechst of Germany. Absorbent surrogate particles, or surrogateparticles having surface cavities or pores, or having pores and surfacecavities, are especially useful as carriers of liquid active substances.Thus, superabsorbent particles and elongated particles havinglongitudinal surface channels may be used as carriers of liquid activesubstances. The foregoing list is intended to be representative of andnot in limitation of labile active substances suitable for use infibrous structures in accordance with the present invention.

In accordance with the invention, after the surrogate particles areimmobilized, a functionally effective amount of the labile activesubstance is deposited on the surrogate particles. The loading of thelabile active substance will vary depending upon factors including theintended function and the comparative effectiveness of the labilesubstance for the intended function. Accordingly, a relatively greateramount of a relatively less effective, labile active substance will beused, whereas a relatively smaller amount of a relatively moreeffective, labile active substance will be appropriate to obtaincomparable functional activity.

In accordance with the invention, the labile active substance isbeneficially selectively deposited on the surrogate particles. By"selective" is meant significantly more deposition on the surrogateparticles than on other available surface of the fibrous structure. Toprovide for selective deposition, the surrogate particles may, asmentioned, have physical structure such as pores providing a useful voidvolume or an irregular surface having surface cavities. Alternatively orin addition, the labile active substance and the surrogate particles maybe specifically attractive to one another. Thus, a variety of methodsand techniques may be selected from, for the selective deposition,depending upon factors including the basis for the selective deposition,the chemical and physical properties of the labile active substance andthe surrogate particles, and the need to maintain the structuralintegrity of the fibrous matrix. Useful active deposition methodologiesinclude sublimation, grafting, plasma treatment, vapor deposition,electrocharging, electrodeposition, liquid phase deposition, chemicalbonding, the use of pressure and/or temperature as the driving force,chemical or physical modification of the surrogate particles, and othersuitable techniques. If heat is applied in a deposition methodology, thetemperature selected should be less than that at which the desiredproduct including the fibrous matrix, is adversely affected. Thedeposition should be efficient to minimize loss of the labile activesubstance.

Depending upon the deposition methodology, the chemical and physicalproperties of the surrogate particles and labile active substance, andother considerations, the labile active substance may be associated withthe surrogate particles in various ways. The labile active substance maybe, for example, merely deposited on the surface of, within pores and/orsurface cavities of, or on the surface and within pores of the surrogateparticles, but in any case not in attractive association with, or bondedor otherwise attached to, the surrogate particles. Associative labilityis typically characterized by this limited type of association.Illustrative is a liquid labile active substance deposited in pores andcavities of surrogate particles, or in surface channels of elongatedsurrogate particles.

The labile active substance may alternatively or additionally be inattractive association with, or physically or chemically bonded orotherwise attached to, the surrogate particles. If chemically bonded,covalent chemical bonding may be an appropriate choice depending uponthe surface chemistry, for instance, bonding sites, of the surrogateparticles, and the chemistry of the labile active substance. To effectattraction or attachment, the surrogate particles and labile activesubstance may be chemically or physically modified to be specificallyattractive to one another. The attraction or attachment between thelabile active substance and the surrogate particles may be reversible sothat after the useful service life, the attraction, for instanceattractive charges, may be "turned off". Reversibility facilitatesrecovery and safe disposal of spent labile active substance withoutaffecting the immobilized surrogate particles-fibrous matrix structure.Thereafter, the activity of the fibrous structure may be regenerated bydeposition of fresh labile active substance.

Optionally, the fibrous structure may also include particles other thanthe surrogate particles, for instance, functionally active particles,i.e., particles having a useful function other than as a mere carrier ina fibrous structure. If so, then these particles will typically beimmobilized. However, if the fibrous structure includes both theseparticles and surrogate particles, then in accordance with theinvention, the labile active substance will be selectively deposited onthe surrogate particles. Thus, by means of a driving force such as apreferential attraction between the surrogate particles and the labileactive substance vis-a-vis any attraction between these particles andthe labile active substance, the selective deposition will be effected.Accordingly, consistent with the need for selective deposition, thefibrous structure may include these particles. If present, thesefunctionally active particles will typically have a different functionalactivity than that of the labile active substance.

The labile active substance may be used alone or with another labileactive substance. The labile active substance may also be used incombination with a relatively stable or stable active substance orsubstances having a beneficial effect; if so, the surrogate particles orthe just-described, optional particles could serve as the carrier. Therelatively stable or stable active substance may produce a useful effectsimilar to that described for a labile active substance; however, thefunctional activity will typically differ from that of the labile activesubstance.

FIG. 1 shows at 20 a sectional view through a non-woven fibrousstructure in accordance with the invention. A plurality of individualstructural fibers 22 form an open web 24, and define an upper surface 26and a lower surface 28 of the web. Beneficially, the fibrous matrix ofthe web is generally uniform and surrogate particles 30 depicted ashaving rough surfaces, are distributed in a generally uniform, threedimensionally spaced apart arrangement within the web. Optionallydeposited within the web structure are functionally active particles 32,illustrated for ease of distinction, as having smooth surfaces.Alternatively, surrogate particles 30 and active particles 32 could bedeposited on the web surface only, on the web surface and within theweb, or in different locations such as active particles 32 on the websurface and the surrogate particles within the web.

In accordance with the invention, surrogate particles 30 arebeneficially immobilized so as to be maintained in the spaced apartrelationship. Likewise advantageously immobilized are active particles32. Attached to surrogate particles 30, but not to particles 32, is alabile active substance, not shown in FIG. 1. Preferential attractionbetween the labile active substance and the surrogate particles benefitsselective deposition. Surrogate particles 30 have pores and cavitieswhich increase the surface area for attractive deposition. Activeparticles 32 have a different functional activity than that of thelabile active substance.

The fibrous structure of FIG. 1 is advantageously dry formed fromcrimped staple macrofiber. Dry forming, and in particular carding,advantageously provides an open, generally uniform fibrous structure,and thereafter for controlled introduction and spacing of surrogateparticles 30 and active particles 32, with accessibility and tortuouspaths in the particle-loaded structure for gas or fluid flow. Surrogateparticles 30 and active particles 32 are of approximately the samedensity and volumetric size; thus, the structure of FIG. 1 may be madeby adding these particles approximately simultaneously to the fibrousstructure. If, on the other hand, the surrogate particles differsignificantly in density and/or size from the active particles, thesurrogate particles will usually be added separately from the activeparticles, typically forming separate layers.

Referring to FIG. 2, an alternative embodiment of a representativesurrogate particle immobilized in a fibrous framework like that of FIG.1, is shown. Corresponding numbers designate like parts, and for sakefor brevity, details previously described are not repeated. In thisembodiment, surrogate particle 30' has pores (represented by dots) andan irregular surface with cavities 40 of varying sizes. In accordancewith the invention, deposited in cavities 40 and pores of the surrogateparticle, is a labile active substance, designated 8 and for sake ofillustration depicted as deposited in the larger cavities. Promotingselective deposition on the surrogate particles vis-a-vis the fibrousmatrix, fibers 22' have relatively smooth surfaces compared to the roughsurface of the surrogate particles. In this embodiment, the fibrousmatrix will typically lack optional particles 32.

Fibers 22' are advantageously sheath/core composite fibers each having acore 56 and a lower melting sheath 58. Surrogate particles arebeneficially bonded to the fibers at numerous points 66, the bondingbeing preferably localized, and fiber-to-fiber bonding at cross overpoints of the fibers stabilizes the web structure. Likewise, the fibrousweb of FIG. 1 is formed of sheath/core composite fibers.

A fibrous structure in accordance with the invention, may have incontact therewith one or more other layers. These layers may benonwovens including partially densified nonwovens and melt blown webs,woven fabrics, knit fabrics, porous membranes and so forth. These layersmay be laminated to or otherwise suitably attached to the inventivefibrous structure, and may exert a useful function if desired.

Uses include filtration such as vehicle cabin air filtration, in-doorair filtration, filtration appliances and liquid filtration. Usesinclude pharmaceutical, medical and biotech processing, food andbeverage processing, and blood processing including of whole blood andblood components. Analytical uses include diagnostic testing. Thefibrous structures may be used as wall coverings with a sorptive and/orodorizing function. Environmental uses include emissions control.Military, civil defense and police uses exist.

The fibrous media may be used as is, or in various forms includingpleated, tubes, pockets (as in pocket filters), blankets, rolls, bags,ducts and ductliners. The fibrous structure may be used singly or incombination with other fabrics, filter media, films, plastics andmembranes.

In a beneficial process for making a fibrous structure in accordancewith the present invention, a carding machine cards crimped fiber andforms an open nonwoven web on an endless moving belt. Surrogateparticles are applied to the web from, for instance, a shaker. The webis open to an appropriate degree and the surrogate particles are ofappropriate size and weight to become entrapped in the interior of theweb. Then, heat in the form of IR heat, may be advantageously applied tothe entire structure under appropriate conditions to provide foradhesion of the surrogate particles to the matrix structure andfiber-fiber bonding. In this way, a fibrous matrix is formed, andthereafter surrogate particles are distributed in a three dimensionalarrangement and immobilized.

Other types of immobilization may be used. A heat-bonding step, if used,is carried out at a sufficient elevated temperature less than themelting point of the structural fiber and for a suitable period of timeto cause adhesion of the surrogate particles to the structural fiber.The fibrous structure is thereafter cooled.

Thereafter, in accordance with the invention, a labile active substanceis added to the surrogate particles/fibrous matrix structure, and isselectively deposited on the surrogate particles. A suitable depositionmethodology is selected consistent with the considerations previouslydescribed. Accordingly, there is also provided a method by which afibrous matrix with immobilized surrogate particles is prepared, andthereafter a labile active substance is selectively deposited on thesurrogate particles using suitable deposition conditions.

The present invention may be carried out with various modificationswithout departing from the spirit or essential attributes thereof, andaccordingly, reference should be made to the appended claims, ratherthan to the foregoing specification as indicating the scope of theinvention.

We claim:
 1. A fibrous structure comprising a fibrous matrix withheat-bonded surrogate particles immobilized in a three dimensionalarrangement, and a labile active substance sensitive to heat bonding,post-immobilization deposited on said surrogate particles.
 2. Thefibrous structure of claim 1, wherein said surrogate particles areporous, and said labile active substance is deposited in the pores ofsaid surrogate particles.
 3. The fibrous structure of claim 1, whereinsaid surrogate particles are porous and have surface cavities, and saidlabile active substance is deposited in the pores and said surfacecavities.
 4. The fibrous structure of claim 1, wherein said surrogateparticles are elongated and each comprises at least one longitudinallydisposed surface channel, and said labile active substance is depositedin said surface channels.
 5. The fibrous structure of claim 1, whereinsaid surrogate particles are selected from the group consisting ofcarbon particles, zeolite particles, alumina particles, polymericparticles and absorbent particles.
 6. The fibrous structure of claim 1,wherein said labile active substance is chemically or physicallyattractively associated with or attached to said surrogate particles. 7.The fibrous structure of claim 6, wherein the attractive association orattachment between said labile active substance and said surrogateparticles is reversible.
 8. The fibrous structure of claim 6, whereinsaid labile active substance is attached to said surrogate particles bychemical bonding.
 9. The fibrous structure of claim 1, furthercomprising particles other than said surrogate particles, theseadditional particles being active particles.
 10. The fibrous structureof claim 1, wherein said three dimensional arrangement is a generallyuniform, three dimensionally spaced apart arrangement.
 11. The fibrousstructure of claim 1, wherein said labile active substance is selectedfrom the group consisting of potassium permanganate, activated manganesedioxide, alkali metal and alkaline earth metal iodates, sorptive organicamines, a substance intended to be released from said surrogateparticles, and polyethyleneglycoldimethylether.
 12. The fibrousstructure of claim 1, wherein said labile active substance is a liquidorganic substance.
 13. A process for making a fibrous structurecomprising a three dimensional arrangement of a labile active substance,said process comprising distributing surrogate particles in a threedimensional arrangement within a fibrous matrix, immobilizing the threedimensionally distributed surrogate particles by heat bonding of saidsurrogate particles, and after the heat bonding, depositing on saidsurrogate particles a labile active substance sensitive to the heatbonding.
 14. The process of claim 13, wherein said surrogate particlesare porous, and said labile active substance is deposited in the poresof said surrogate particles.
 15. The process of claim 13, wherein saidsurrogate particles are porous and have surface cavities, and saidlabile active substance is deposited in the pores and said surfacecavities.
 16. The process of claim 13, wherein said surrogate particlesare elongated and each comprises at least one longitudinally disposedsurface channel, and said labile active substance is deposited in saidsurface channels.
 17. The process of claim 13, wherein said surrogateparticles are selected from the group consisting of carbon particles,zeolite particles, alumina particles, polymeric particles and absorbentparticles.
 18. The process of claim 13, wherein said three dimensionalarrangement is a generally uniform, three dimensionally spaced apartarrangement.
 19. The process of claim 13, wherein said labile activesubstance is selected from the group consisting of potassiumpermanganate, activated manganese dioxide, alkali metal and alkalineearth metal iodates, sorptive organic amines, a substance intended to bereleased from said surrogate particles, andpolyethyleneglycoldimethylether.
 20. The process of claim 13, whereinparticles other than said surrogate particles are deposited within saidfibrous framework, these additional particles being active particles;wherein at least one other layer is disposed on or within said fibrousstructure; and wherein said labile active substance is a liquid organicsubstance.